The Food and Drug Administration has recalled millions of bottles of widely-used blood pressure medicines after a cancer-causing contaminant was found. (AP Photo/Andrew Harnik, File)
Federal
regulators say they’ve identified the source of the cancer-causing
impurities that have tainted millions of bottles of commonly used
generic blood pressure and heart failure medications recalled by drugmakers over the last seven months.
The carcinogens are a chemical byproduct of the process used to synthesize the active ingredient in the drugs, which include valsartan, losartan
and irbesartan. People who take those drugs may have been exposed to
trace amounts of impurities for at least four years, after a switch in
how companies manufactured the active ingredient, according to the Food
and Drug Administration.
An FDA statement Friday
disclosed that the contaminants, called N-Nitrosodimethylamine and
N-Nitrosodiethylamine, are created when “specific chemicals and reaction
conditions are present . . . and may also result from the reuse of
materials, such as solvents.” The agency said those byproducts would not
have been detected in routine inspections because the process depends
on scientists knowing which chemical intruders are likely to be
accidentally created during the process, knowledge that they said
regulators and companies lacked until recently.
But
David Light, chief executive of Valisure, an online pharmacy that
chemically validates drugs before shipping them to consumers, said it’s
possible that companies weren’t cleaning up the active ingredients as a
cost-saving measure. It wouldn’t have been unexpected, he said, that the
synthesis process would create contaminants.
“In
chemistry, it’s pretty easy to throw some chemicals together and get a
reaction,” Light said. “What’s hard to do is to clean it up and only get
the product you want . . . . The manufacturers know, or should have
known, about the contamination. Common precision tools exist to analyze
these contaminants, and there are standard procedures for getting rid of
them.”
It remains unclear how many patients may
have been exposed to the carcinogens, but agency leaders have
previously estimated that 1 million to 2 million people may have taken
the medicines with the impurities.
“We
are making important strides at understanding how these impurities
occurred, mitigating the risk to patients and learning what steps need
to be taken to prevent this from occurring again in the future,”
Commissioner Scott Gottlieb and Center for Drug Evaluation and Research
director Janet Woodcock said in a statement. “While the total exposure
to these impurities for most patients was small, we are deeply concerned
that patients were exposed to this impurity in the first place and that
the presence of nitrosamines went undetected for a period of time."
The
agency has downplayed the public health risks of the contamination,
pointing out that if 8,000 people took the highest dose of one drug,
valsartan, for four years, there could be one additional case of cancer.
The carcinogens are found in smoked and grilled meats. But the official
limit considered “safe” for human consumption brings a much lower risk
than the possible exposure from tainted drugs — causing less than one
additional case of cancer in 100,000 people over a lifetime.
The
unfolding investigation shines a light on the dark corners of a
complex, international drug supply chain — and in particular the
difficulties that can crop up when safety issues arise for generic
drugs, which may be made by multiple drug manufacturers and repackagers
that may use active ingredients from one factory or a small handful of
them.
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